M-DNA/Transition Metal Dichalcogenide Hybrid Structure-based Bio-FET sensor with Ultra-high Sensitivity

Here, we report a high performance biosensor based on (i) a Cu²⁺-DNA/MoS₂ hybrid structure and (ii) a field effect transistor, which we refer to as a bio-FET, presenting a high sensitivity of 1.7 × 10³ A/A. This high sensitivity was achieved by using a DNA nanostructure with copper ions (Cu²⁺) that induced a positive polarity in the DNA (receptor). This strategy improved the detecting ability for doxorubicin-like molecules (target) that have a negative polarity. Very short distance between the biomolecules and the sensor surface was obtained without using a dielectric layer, contributing to the high sensitivity. We first investigated the effect of doxorubicin on DNA/MoS₂ and Cu²⁺-DNA/MoS₂ nanostructures using Raman spectroscopy and Kelvin force probe microscopy. Then, we analyzed the sensing mechanism and performance in DNA/MoS₂- and Cu²⁺-DNA/MoS₂-based bio-FETs by electrical measurements (I_D-V_G at various V_D) for various concentrations of doxorubicin. Finally, successful operation of the Cu²⁺-DNA/MoS₂ bio-FET was demonstrated for six cycles (each cycle consisted of four steps: 2 preparation steps, a sensing step, and an erasing step) with different doxorubicin concentrations. The bio-FET showed excellent reusability, which has not been achieved previously in 2D biosensors.